In the related art, an image forming apparatus has been known which is configured to rotate a photosensitive member in a reverse direction on re-conveyance of conveying a sheet with being inverted during a duplex printing. Specifically, according to this technology, when forming an image on the sheet, the photosensitive member is rotated in a forward direction and a transfer bias of a first polarity is applied to a transfer device. After forming an image on a first surface of the sheet, when a conveying direction of the sheet is switched, the photosensitive member is rotated in a reverse direction.
During a time period in which the photosensitive member is rotated in the reverse direction, the transfer bias is set to OFF or a bias of a second polarity in opposite to the first polarity so that developer is not to move from the photosensitive member to the transfer device. After switching the photosensitive member from the reverse rotation to the forward rotation, the transfer bias is set to the bias of the first polarity.
However, when switching the rotation direction of the photosensitive member from the reverse direction to the forward direction, the developer may be attached to a part, which faces a developing roller, of the photosensitive member.